A prior art device is described in EP 1004 373 B1. Such devices are used to mold internal toothing onto work pieces, in particular rings for planetary gearing. By setting press rollers against the preform, material is displaced from said preform against the negative form of the spinning mandrel. In this process, the acting forces act on the outer toothing of the spinning mandrel such that the teeth can break. The prior art recommends providing a spacer ring made of moldable material at a distance from the free end of the spinning mandrel. In the forming process, the moldable spacer ring adapts to the outer profile of the spinning mandrel. Thus, the spacer ring assumes at least in part the forces that come into existence during the forming process.
The disadvantage is that a spacer ring and a parallel key are always required, complicating the arrangement. In addition, high forming temperatures occur that significantly increase the time for forming and manufacturing the work pieces.